CVE-2024-41948

biscuit-java is the java implementation of Biscuit, an authentication and authorization token for microservices architectures. Third-party blocks can be generated without transferring the whole token to the third-party authority. Instead, a ThirdPartyBlock request can be sent, providing only the necessary info to generate a third-party block and to sign it, which includes the public key of the previous block (used in the signature) and the public keys part of the token symbol table (for public key interning in datalog expressions). A third-part block request forged by a malicious user can trick the third-party authority into generating datalog trusting the wrong keypair. This vulnerability is fixed in 4.0.0.

biscuit-java is the java implementation of Biscuit, an authentication and authorization token for microservices architectures. Third-party blocks can be generated without transferring the whole token to the third-party authority. Instead, a ThirdPartyBlock request can be sent, providing only the necessary info to generate a third-party block and to sign it, which includes the public key of the previous block (used in the signature) and the public keys part of the token symbol table (for public key interning in datalog expressions). A third-part block request forged by a malicious user can trick the third-party authority into generating datalog trusting the wrong keypair. This vulnerability is fixed in 4.0.0.

Impact

Tokens with third-party blocks containing trusted annotations generated through a third party block request. Due to implementation issues in biscuit-java, third party block support in published versions is inoperating. Nevertheless, to synchronize with other implementations, we publish this advisory and the related fix.

Description

Third-party blocks can be generated without transferring the whole token to the third-party authority. Instead, a ThirdPartyBlock request can be sent, providing only the necessary info to generate a third-party block and to sign it:

the public key of the previous block (used in the signature) the public keys part of the token symbol table (for public key interning in datalog expressions) A third-part block request forged by a malicious user can trick the third-party authority into generating datalog trusting the wrong keypair.

Consider the following example (nominal case)

• Authority A emits the following token: check if thirdparty("b") trusting ${pubkeyB}
• The well-behaving holder then generates a third-party block request based on the token and sends it to third-party authority B
• Third-party B generates the following third-party block thirdparty("b"); check if thirdparty("c") trusting ${pubkeyC}
• The token holder now must obtain a third-party block from third party C to be able to use the token

Now, with a malicious user:

• Authority A emits the following token: check if thirdparty("b") trusting ${pubkeyB}
• The holder then attenuates the token with the following third party block thirdparty("c"), signed with a keypair pubkeyD, privkeyD) they generate
• The holder then generates a third-party block request based on this token, but alter the ThirdPartyBlockRequest publicKeys field and replace pubkeyD with pubkeyC
• Third-party B generates the following third-party block thirdparty("b"); check if thirdparty("c") trusting ${pubkeyC}
• Due to the altered symbol table, the actual meaning of the block is thirdparty("b"); check if thirdparty("c") trusting ${pubkeyD}
• The attacker can now use the token without obtaining a third-party block from C.

Patches

Has the problem been patched? What versions should users upgrade to?

Workarounds

Is there a way for users to fix or remediate the vulnerability without upgrading?

References

Are there any links users can visit to find out more?

biscuit-java is the java implementation of Biscuit, an authentication and authorization token for microservices architectures. Third-party blocks can be generated without transferring the whole token to the third-party authority. Instead, a ThirdPartyBlock request can be sent, providing only the necessary info to generate a third-party block and to sign it, which includes the public key of the previous block (used in the signature) and the public keys part of the token symbol table (for public key interning in datalog expressions). A third-part block request forged by a malicious user can trick the third-party authority into generating datalog trusting the wrong keypair. This vulnerability is fixed in 4.0.0.

biscuit-java is the java implementation of Biscuit, an authentication and authorization token for microservices architectures. Third-party blocks can be generated without transferring the whole token to the third-party authority. Instead, a ThirdPartyBlock request can be sent, providing only the necessary info to generate a third-party block and to sign it, which includes the public key of the previous block (used in the signature) and the public keys part of the token symbol table (for public key interning in datalog expressions). A third-part block request forged by a malicious user can trick the third-party authority into generating datalog trusting the wrong keypair. This vulnerability is fixed in 4.0.0.

Impact

Tokens with third-party blocks containing trusted annotations generated through a third party block request. Due to implementation issues in biscuit-java, third party block support in published versions is inoperating. Nevertheless, to synchronize with other implementations, we publish this advisory and the related fix.

Description

Third-party blocks can be generated without transferring the whole token to the third-party authority. Instead, a ThirdPartyBlock request can be sent, providing only the necessary info to generate a third-party block and to sign it:

the public key of the previous block (used in the signature) the public keys part of the token symbol table (for public key interning in datalog expressions) A third-part block request forged by a malicious user can trick the third-party authority into generating datalog trusting the wrong keypair.

Consider the following example (nominal case)

• Authority A emits the following token: check if thirdparty("b") trusting ${pubkeyB}
• The well-behaving holder then generates a third-party block request based on the token and sends it to third-party authority B
• Third-party B generates the following third-party block thirdparty("b"); check if thirdparty("c") trusting ${pubkeyC}
• The token holder now must obtain a third-party block from third party C to be able to use the token

Now, with a malicious user:

• Authority A emits the following token: check if thirdparty("b") trusting ${pubkeyB}
• The holder then attenuates the token with the following third party block thirdparty("c"), signed with a keypair pubkeyD, privkeyD) they generate
• The holder then generates a third-party block request based on this token, but alter the ThirdPartyBlockRequest publicKeys field and replace pubkeyD with pubkeyC
• Third-party B generates the following third-party block thirdparty("b"); check if thirdparty("c") trusting ${pubkeyC}
• Due to the altered symbol table, the actual meaning of the block is thirdparty("b"); check if thirdparty("c") trusting ${pubkeyD}
• The attacker can now use the token without obtaining a third-party block from C.

Patches

Has the problem been patched? What versions should users upgrade to?

Workarounds

Is there a way for users to fix or remediate the vulnerability without upgrading?

References

Are there any links users can visit to find out more?